Protective device



K. a. common 2,264,130 RROIBC'I'I VB DEVICE Nov. 2 5, 1941'.

Filed on. 19. 1940 FIG/ /////,S. y, I?

IIIIIIIIII/ IIIII'IIIIIIIII IIIlI/I/Mfl EQUIVALENT CIRCUIT /N 5 N TOR K. G. COMP TON BY Patented Nov. 25, 1941 'PROTECTIVEDEVICE Kenneth G. Compton, Madison, N, J., assignor to Bell Telephone Laboratories, Incorporated,

New York, N. Y., a corporation of New York Application October 19, 1940, Serial No. 361,877

1 Claim. "(CL 175-415) This invention relatesto a protective device for relay contacts and the like.

It is customary in the art for reducing sparking in the make and break of electrical relay con- Y tacts to provide in a shunt path around the contacts a condenser in series with a resistance of appropriate values. In many instances such as in the telephone plant where a large number of relays may be mounted in a restricted space in close proximity to each other the additional space required for the condensers and resistances is a serious factor. i

' In accordance with this invention the space requirement for each resistance-condenser combination is considerably reduced by employing an electrolytic condenser of cylindrical construction and by placing the resistance element within the inner cylinder of the condenser so that the space requirement for the combination is no greater than that for the condenser element alone.

Referring to the drawing:

Fig. l is a view partly in ection of the condenser-resistance unit of this invention;

Fig. 2 is a view in perspective of the resistance element and the inner cylinder of the condenser;

and"

Fig. 3 shows the electrical circuit of the combination.

The condenser element of this invention is com posed of two concentric cylinders 4 and 5 pref erably of aluminumseparated by a paper cylinder 6 impregnatedwith a suitable electrolyte such as is commonly used in dry type electrolytic condenser as, for example, a compound or mixture of boric acid, or its derivatives with ethyl ene glycol or other polyhydric alcohol. Prior to end with:the'carbongranulcs H sprayed, on the outer surface of the glass cylinder 8 in an-gamount sufficient to'give the desired resistance value between terminals 9 and HI.

After connecting lead wires 12 and I3 to the resistor terminals 9 and ID the resistor is in serted in the open end of inner cylinder 5 with one end of wire [2 connected to the inner wall of cylinder 5, for example, at the point. The resistor 8 is preferably held concentrically in place within cylinder 5 and spaced from the inner walls and the closed end of cylinder 5 by means of inassembly, the external surface of the inner cylinder 5 is formed to the desired voltage in an electrolytic bath to produce on its external surface a film l of aluminum oxide (which film is shown with an exaggerated thickness in both Figs. 1 and 2) whereupon the cylinder 5 is washed to remove all traces of the forming electrolyte. The inner cylinder 5 is then ready to be assembled within the outer cylinder 4 along with the porous paper spacer cylinder 6 after which the spacer cylinder 6 may be impregnated with a viscous electrolyte. After impregnation, the electrolyte is flushed out of the interior of the inner cylinder 5.

The resistance element is preferably of the sprayed carbon type of a length and diameter substantially less than the corresponding dimensions of the inner cylinder 5. As shown, the resistance element comprises a tubular member 8 of a suitable dielectric material such as glass having conductive members 9 and In at either I rial substantially filling the space between saidv sulating material l5 such asan asphaltic sealing compound. I v

The paper cylinder 6 preferably has a closed end spacing, the closed end l6 of the inner aluminum cylinder from the closed end I"! of the outer aluminum cylinder a distance substantially the same as the distance between cylinders 4 and 5; and the inner cylinder 5 is preferably somewhat longer than the outer cylinder as is evident from Fig. 1.

The outer cylinder 4 is p eferably slightly taperecl at its open endl8 over which is forced a tightly fitting metal cap I9. Between the end of cap l9 and the open end of inner cylinder 5 is a fibre washer '20 which centrally supports a suitable terminal 2| connected to wire 13, which terminal passesthrough an aperture 22 in the end ofmetal cap .13. ,As shown'in Fig. 1 the asphaltic compound l5 completely fills, the inner cylinder 5 and also fills the space between cylin-' der 5 and cap I9. r

In connecting the ,resi'stanceecondenser device of Fig' l into the desired circuit, conductor 2| m'ay serve asone terminal and conductor 23 as the otherterminalxto provide in series a conprising a cylindrical container formingthe cathode, an anode comprising a cylinder of film form'- ing metal within said container and spaced from the inner wall of said container, an electrolyte between said anode and said container, an elongated electrical resistance element within said anode and substantially aligned with the axis of said anode, and a packing of insulating mateelement and the inner surface of said anode for supporting said element in spaced relation to said anode.

. KENNETH G. COMPTON.

sprayed car- 

